This project is designed to evaluate the use of testosterone enanthate for induction of reversible azoospermia. In addition to periodic semen examinations, fasting blood sugar, triglyceride, cholesterol, lipoprotein, and plasma LH and FSH and testosterone will be determined. Studies will be continued as follows: control period, eight weeks; 200 mg of testosterone enanthate IM weekly for eight weeks regardless of semen findings; 200 mg of testosterone enanthate IM every three weeks for 44 weeks; and recovery period, six months with reevaluation three months later. The study will cover observation of tweny fertile healthy males aged 25-45.